Thermite-Metal Foam

ABSTRACT

The present invention discloses materials, systems and methods for creating metal foams to envelop targets, which involve the formulation of powdered thermite/metal matrices. Essentially, each matrix will include thermite and a foaming agent. Additionally, a thickening agent can be blended into the powdered thermite/metal matrix to create desirable foaming properties when the thermite is ignited. A heat sink agent can also be dispersed throughout the powdered thermite/metal matrix to limit temperature rise in the matrix during a thermite reaction. Further, a binder can be combined with the powdered thermite/metal matrix to hold the formulation together. In use, the formulation is delivered to the vicinity of the target where it is ignited. The resultant metal foam is intended to envelop and neutralize the target.

FIELD OF THE INVENTION

The present invention pertains generally to materials, systems andmethods for creating metal foams. More particularly, the presentinvention pertains to formulations wherein a foaming agent is combinedwith thermite to create a metal foam in response to an ignition ofthermite. The present invention is particularly, but not exclusively,useful as a material, system and method for enveloping and neutralizingchemical and biological (C/B) warfare agent weapons and facilities.

BACKGROUND OF THE INVENTION

It is well known that many chemical and biological (C/B) agents are, bydesign, toxic or very hazardous materials. When released, they can bedispersed over a wide area where they pose serious threats to life andproperty. To prevent such potential situations, it is essential thatenemy access to C/B agent storage and production facilities be deniedwhile also ensuring the agents be somehow neutralized or destroyed.Often this requires immediate action under circumstances (e.g. combat)that are not conducive to a more methodical operation. Conventionalexplosive munitions have been considered as an immediate response.Explosive munitions, however, can exacerbate the situation bycontributing to an unwanted dispersal of the C/B agents.

An effective way of denying access to C/B agents is to envelop them in amanner that will prevent their further dispersal. Specifically, such arestrictive confinement requires enveloping the C/B materials within arigid barrier. Preferably, as alluded to above, this process can beaccomplished quickly and efficiently under hostile conditions, withoutdispersing the C/B agents.

Any of several types of well known metal foams may be suitable for thepurpose of enveloping C/B materials. In particular, foams generallyknown as closed cell foams are preferable in order to minimize thechance of agent release. The creation of such foams, however, typicallyrequires elevated temperatures. In the context of a system for creatinga metal foam that can be used to confine and neutralize C/B materials(i.e. where the system is an Agent Defeat Weapon), the metal foam ispreferably created by a heat-activated-chemical (HAC) method that willgenerate the required elevated temperatures. Thermite provides such anHAC method.

In the most common form of thermite, aluminum-iron (III) oxide, aluminum(Al) reduces the iron oxide to produce a large exothermic heat ofreaction and molten iron. The reaction is:

Fe₂O₃+2Al

2Fe+Al₂O₃+Heat

Operational temperatures in excess of 2000° C. have been developed withthe above stated reaction.

In light of the above, it is an object of the present invention toprovide an HAC material, system and method for creating a metal foamthat envelops and neutralizes a target thought to include C/B agents.The target may include warehoused or stored munitions, bulk materials,and/or manufacturing facilities and supplies related to C/B agents.Another object of the present invention is to provide a system andmethod for creating a metal foam that can be used to render C/Bmaterials unusable by virtue of the solidified metal foam adhering tosurfaces of the C/B material containers or facilities. Still anotherobject of the present invention is to provide a material, system andmethod for creating a metal foam in response to the ignition of athermite powder formulation. Yet another object of the present inventionis to provide a material, system and method for creating a metal foamthat is easy to use, simple to manufacture, and cost effective.

SUMMARY OF THE INVENTION

In accordance with the present invention, a material, system and methodfor creating a metal foam are provided. Specific purposes for this metalfoam are to envelop and neutralize C/B targets or to disable facilitiesand munitions. In detail, a formulation for creating the metal foamincludes thermite, and a foaming agent that is admixed with thethermite. Together the resultant formulation creates a powderedthermite/metal matrix. In addition to the molten iron inherent to thereacting thermite, secondary melt-forming metals may be included in theformulation to adjust the necessary foaming conditions, such astemperature. The formulation may also include a thickening agent that isblended into the powder matrix (formulation) to provide the mostfavorable foaming properties as the thermite reacts. Additionally, thepowder matrix (formulation) can include a heat sink agent that isdispersed throughout the powder matrix to moderate the temperature ofthe matrix during the thermite reaction. The powder matrix may alsoinclude a binder that is combined with the matrix for holding theconstituents together.

As envisioned for the present invention, the thermite preferablycomprises an aluminum (Al) powder fuel component having particles withdiameters in a range of about three to one hundred and thirty microns(3-130 microns). The thermite will also include an iron oxide oxidantpowder having particles less than about one micron (<1 micron) indiameter. In the preferred embodiment, the oxidant may be either redFe₂O₃ or black Fe₃O₄. In the case of red Fe₂O₃, the aluminum (Al) andiron oxide will typically be mixed together in a weight ratio ofapproximately 8:3. For black Fe₃O₄, a weight ratio of approximately 3:1will typically be used.

Alternative formulations for the thermite are also envisioned for thepresent invention. For example, the formulation may contain excess Alover that described in the preceding paragraph, resulting in a mixtureof molten iron and aluminum that may be more easily foamed. In otheralternate embodiments, the Al fuel component of the thermite can bereplaced with Mg, Ca, Ti, Zn, Si or B. Further, along with thereplacements for Al, the oxidant for alternate embodiments of thethermite can be selected from a group consisting of B₂O₃, SiO₂, Cr₂O₃,MnO₂ and CuO.

For the present invention, the foaming agent (a.k.a. blowing agent) maybe selected from a group consisting of FeO+C, SrCO₃, VO₂+C, Cr₂O₃+C,MnO+C and TiH₂. In particular, the content of the foaming agent in theformulation will be, for example, less than about 2.5 wt % of the metalfoam, and the foaming agent will be made of particles having diametersin the range of one to two microns (1-2 microns). The thickening agentmay be selected from a group consisting of SiC, Al₂O₃ and MgO.Typically, the thickening agent will be about 10-30 wt % of the metalfoam and will be made up, for example, of particles of five to twentymicrons (5-20 microns) in diameter. The heat sink agent may be TiC andwill, for example, be less than about 10 wt % of the metal foam. In thepowder formulation, the heat sink agent will have particle sizes betweenone and three microns (1-3 microns). As mentioned above, the powderformulation may include a binder. If so, the binder will typically beselected from a group consisting of KBr, NaBr, CaBr₂ and S. The binderwill normally be between about 5-8 wt % of the metal foam and, in thepowder formulation, will have particle sizes of about 5 micronsdiameter.

In the preceding concept, the metal foam is formed from the molten ironphase that results from the thermite reaction. In an alternative binarymunition concept, the thermite constituents and metal foam constituentsare not mixed together but, instead, packaged side-by-side. Heat fromthe thermite reaction is transferred to the foam forming mixture,allowing formation of foam from a molten phase other than thatassociated with the thermite reaction.

When used in a system, the powder formulation is placed in a canisterand an igniter is provided to initiate a reaction in the formulation.This reaction will then create the metal foam. In use, the canisterholding the formulation can be deployed to the C/B target by any ofseveral means. Examples of possible delivery means include: manned orunmanned aircraft, rocket or artillery delivery systems, and handdelivery. The delivery means may include apparatus for dispersing thefoam or foam forming constituents or canisters. Regardless of how it maybe delivered, when ignited at or approaching the target, the formulationturns into a molten metal foam that surrounds and envelops the target.In this process, as the metal foam is enveloping the target, it freezesto envelop and neutralize the target.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of this invention, as well as the invention itself,both as to its structure and its operation, will be best understood fromthe accompanying drawings, taken in conjunction with the accompanyingdescription, in which similar reference characters refer to similarparts, and in which:

FIG. 1 is a visualization of the components used for making aformulation and a delivery system for the present invention;

FIG. 2 is a Table showing accessible variables for use in a manufactureof the formulation for the present invention;

FIG. 3A is a perspective view of a system in accordance with the presentinvention, with the system shown positioned adjacent to a C/B targetprior to envelopment of the C/B material by the system; and

FIG. 3B is a perspective view of the C/B material shown in FIG. 3A afterenvelopment by the system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1, a formulation 10 for the presentinvention is shown to include both essential ingredients 12 andadditives 14. During a manufacture of the formulation 10, both theessential ingredients 12 and the additives 14 will be in a powder form.Thus, the formulation 10 that results from mixing ingredients 12 withadditives 14 will be essentially a powdered thermite/metal matrix.

In accordance with the present invention, the essential ingredients 12of the formulation 10 are thermite 16 and a foaming agent 18. Further,the thermite portion of the formulation 10 will include both a metalcomponent and an oxidant. Preferably, the component is a metal such asAl, and the oxidant is an iron oxide that can be either Fe₂O₃ or Fe₃O₄.There are, however, possible alternatives for the metal component Al.Also, there are possible alternatives for the oxidant (Fe₂O₃ or Fe₃O₄).For example, Al can be selectively replaced by Mg, Ca, Ti, Zn, Si or B,and the oxidant can be selectively replaced by B₂O₃, SiO₂, Cr₂O₃, MnO₂or CuO. Additional details about these constituents of the thermite 16,as well as details for other possible constituents of the formulation10, are set forth in the Table provided in FIG. 2.

Insofar as possible additives 14 for the formulation 10 are concerned,they may include a thickening agent 20, a heat sink agent 22, and abinder 24. Specifically, in order, the thickening agent 20 can beprovided for the purpose of increasing the viscosity of the molten metalthat results during a thermal reaction of the formulation 10.Specifically, if used, the thickening agent 20 will help the moltenmetal maintain suitable characteristics as it is being transformed intoa metallic foam 26 (see FIG. 3B). For purposes of the present invention,the thickening agent 20 can be selected from a group comprised of SiC,Al₂O₃ and MgO. Next, the heat sink agent 22 can be provided to avoidexcessive temperature within the formulation 10 and is, for example,TiC. And, finally, the binder 24 can be used to provide cohesion to thebody of formulation 10. It (i.e. the binder 24) will preferably beselected from a group comprised of KBr, NaBr, CaBr₂ and S.

Still referring to FIG. 1, it will be appreciated that after theformulation 10 has been prepared (i.e. manufactured by mixing togetherits constituent powders), the formulation 10 can be placed in a canister28. Further, an igniter 30 can be provided to initiate an ignition ofthe thermite 16 in the formulation 10. For purposes of the presentinvention, the igniter 30 is, for example, of a type that will create amagnesium spark of sufficient effect to ignite the thermite 16.

In use, a canister 28 that has been filled with the formulation 10 issomehow positioned in near proximity to a target 32 as shown in FIG. 3A.The actual delivery of the canister 28 to the site of the target 32 canbe accomplished in any of several ways. For example, aircraft, missiles,rockets, conventional artillery, land vehicles, or ground troops may beused to position the canister 28. In any event, once the canister 28 hasbeen positioned (see FIG. 3A), the igniter 30 is activated. With thisactivation, a reaction in the formulation 10 is initiated. Specifically,the molten metal generated by the thermite 16 during this reaction willinteract with the foaming agent 18 to create a metal foam 26. Asintended for the present invention, the metal foam 26 that is aconsequence of this reaction will surround and envelop the target 32(see FIG. 3B). Thus, the target 32 is disabled, neutralized or otherwiserendered unusable. In addition, the heat from the thermite reaction canlead to desirable decomposition/deactivation reactions within the agentcontainer.

Note that in some cases, it may be advantageous to initiate the foamingreaction while the device is still en route to the target to alloweffective dispersal and envelopment from above. Furthermore, thedelivery device may advantageously contain multiple submunitions anddispersal methods to facilitate more effective dispersal of the foamforming charges.

In an alternative binary munition concept, the thermite constituents andmetal foam constituents are not mixed together but arrangedside-by-side. Heat from the ignited thermite reaction is transferred tothe foaming composition, allowing formation of foam from a molten phaseother than that associated with the thermite reaction. This embodimentcan enable the use of lower-temperature molten metals that are easier tofoam and less prone to penetrate the agent container, hence reducing thechance of unintended agent release.

While the particular Thermite-Metal Foam as herein shown and disclosedin detail is fully capable of obtaining the objects and providing theadvantages herein before stated, it is to be understood that it ismerely illustrative of the presently preferred embodiments of theinvention and that no limitations are intended to the details ofconstruction or design herein shown other than as described in theappended claims.

1. A system for creating a metal foam to envelop a target, the systemincluding a formulation for creating the metal foam which comprises:thermite; and a foaming agent positioned with the thermite andresponsive thereto to create the metal foam.
 2. A system as recited inclaim 1 wherein the foaming agent is admixed with the thermite to createa powdered thermite/metal matrix.
 3. A system as recited in claim 1further comprising a thickening agent positioned with the powderedthermite/metal matrix to facilitate action of the foaming agent upon anignition of the thermite.
 4. A system as recited in claim 3 wherein thethickening agent is selected from a group consisting of SiC, Al₂O₃ andMgO.
 5. A system as recited in claim 1 further comprising a heat sinkagent positioned with the powdered thermite/metal matrix.
 6. A system asrecited in claim 5 wherein the heat sink agent is TiC.
 7. A system asrecited in claim 1 further comprising a binder combined with thepowdered thermite/metal matrix for holding the formulation together. 8.A system as recited in claim 7 wherein the binder is selected from agroup consisting of KBr, NaBr, CaBr₂ and S.
 9. A system as recited inclaim 1 wherein the thermite comprises aluminum and iron oxide mixed ina weight ratio of approximately 8:3.
 10. A system as recited in claim 1wherein the foaming agent is selected from a group consisting of FeO+C,SrCO₃, VO₂+C, Cr₂O₃+C, MnO+C and TiH₂.
 11. A system as recited in claim1 wherein the thermite includes a fuel component and an oxidant, whereinthe fuel component is selected from a group consisting of Mg, Ca, Ti,Zn, Si and B, and wherein the oxidant is selected from a groupconsisting of B₂O₃, SiO₂, Cr₂O₃, MnO₂ and CuO.
 12. A system as recitedin claim 1 further comprising: an igniter for initiating a reaction inthe formulation to create the metal foam; and a canister for holding theformulation and the igniter during deployment of the system to thetarget.
 13. A system for neutralizing a target which comprises: apowdered matrix formulation containing thermite and a foaming agent; anigniter for initiating a reaction in the formulation to create a metalfoam for enveloping the target; and a canister for holding theformulation and the igniter during deployment of the system to thetarget.
 14. A system as recited in claim 13 wherein the formulationfurther comprises: a thickening agent; a heat sink agent; and a binder.15. A system as recited in claim 13 wherein the target is selected froma group comprising chemical/biological agents, weapons and facilities.16. A system as recited in claim 13 wherein the igniter initiates thereaction with a magnesium spark.
 17. A system as recited in claim 13wherein the thermite comprises aluminum (Al) and an iron oxide selectedfrom a group consisting of Fe₂O₃ and Fe₃O₄, and further wherein thealuminum and iron oxide are mixed with approximately equal volumes. 18.A method for neutralizing a target which comprises the steps of:delivering a powdered thermite/metal matrix formulation proximate thetarget; igniting the powdered formulation to generate a molten metal;expanding the molten metal with a foaming agent to establish a moltenmetal foam for enveloping the target; and freezing the molten metal tocreate a solid metal foam for enveloping the target.
 19. A method asrecited in claim 18 wherein the thermite/metal matrix comprises aluminum(Al) and an iron oxide selected from a group consisting of Fe₂O₃ andFe₃O₄, and wherein the aluminum and iron oxide are mixed withapproximately equal volumes.
 20. A method as recited in claim 18 furthercomprising the step of blending a thickening agent into the powderedthermite/metal matrix to facilitate action of the foaming agent upon anignition of the thermite.
 21. A method as recited in claim 18 furthercomprising the step of dispersing a heat sink agent throughout thepowdered thermite/metal matrix to control temperature rise therein. 22.A method as recited in claim 18 further comprising the step of combininga binder with the powdered formulation to hold the formulation together.23. A combination of materials for creating a metal foam to envelop atarget, the materials comprising: thermite; and a foaming agentpositioned with the thermite and responsive thereto to create the metalfoam.
 24. A combination of materials as recited in claim 23 wherein thefoaming agent is admixed with the thermite to create a powderedthermite/metal matrix.
 25. A combination of materials as recited inclaim 23 further comprising a thickening agent positioned with thepowdered thermite/metal matrix to facilitate action of the foaming agentupon an ignition of the thermite.
 26. A combination of materials asrecited in claim 25 wherein the thickening agent is selected from agroup consisting of SiC, Al₂O₃ and MgO.
 27. A combination of materialsas recited in claim 23 further comprising a heat sink agent positionedwith the powdered thermite/metal matrix.
 28. A combination of materialsas recited in claim 27 wherein the heat sink agent is TiC.
 29. Acombination of materials as recited in claim 23 further comprising abinder combined with the powdered thermite/metal matrix for holding theformulation together.
 30. A combination of materials as recited in claim29 wherein the binder is selected from a group consisting of KBr, NaBr,CaBr₂ and S.
 31. A combination of materials as recited in claim 23wherein the thermite comprises aluminum and iron oxide mixed in a weightratio of approximately 8:3.
 32. A combination of materials as recited inclaim 23 wherein the foaming agent is selected from a group consistingof FeO+C, SrCO₃, VO₂+C, Cr₂O₃+C, MnO+C and TiH₂.
 33. A combination ofmaterials as recited in claim 23 wherein the thermite includes a fuelcomponent and an oxidant, wherein the fuel component is selected from agroup consisting of Mg, Ca, Ti, Zn, Si and B, and wherein the oxidant isselected from a group consisting of B₂O₃, SiO₂, Cr₂O₃, MnO₂ and CuO.